Step by step
Upload the file instead of attaching it
Drag the file or folder from File Explorer or Finder into the uploader on this page.
Choose expiry and protection
Pick how long the link should work, and add a password or download limit for anything confidential.
Copy the link
When the upload finishes, copy the share link. The 6-digit code is a backup if a mail filter breaks the link.
Paste it into your Outlook email
Write your message as usual and paste the link in the body. The recipient downloads the original file in their browser.
Outlook's limit is a little lower than many people expect, and on work accounts it can be lower still. If you have just seen "attachment size exceeds the allowable limit", this page explains why and gives you a way around it that does not involve shrinking your files.
Outlook limits at the time of writing
| Outlook version | Typical attachment limit |
|---|---|
| Outlook.com (personal Microsoft account) | 20 MB per message |
| Outlook desktop app (Windows, Mac) with a personal account | 20 MB typical |
| Outlook with work or school Exchange / Microsoft 365 | Set by the organisation's admin, may differ |
| Recipient on another provider | Their own incoming limit applies too |
A few things make the practical limit lower than the number on paper:
- The limit covers the whole message, including every attachment and the email body.
- Encoding inflates attachments. Email converts files into text for transport, which adds roughly a third to their size. An 18 MB file on disk may already be too big.
- The other side matters. Even if your server lets a large message out, the recipient's server can reject it.
Microsoft adjusts these numbers from time to time, and corporate settings vary a lot, so the error message you see in Outlook is the real authority.
Work accounts: the admin decides
If you use Outlook at work, the attachment limit comes from your organisation's Exchange or Microsoft 365 settings. Some companies raise it, others lower it to keep mailboxes small. Some also block certain file types or strip attachments from external mail.
Before you work around it, check whether your company has a policy for sharing large files. Many prefer you use their own OneDrive or SharePoint for anything internal. For files going to people outside the company, ask whether external transfer services are allowed.
Three ways past the 20 MB wall
1. Share from OneDrive
Outlook can insert a OneDrive link instead of an attachment. This is a good fit if the recipient is a colleague in the same organisation, since sharing permissions work smoothly. For outside recipients, you need to check that the link is set to allow people outside your organisation, and the file stays in your OneDrive until you clean it up.
2. Compress and split
Zip the files, and if that is still too big, split the archive into parts under 20 MB and send them in separate emails. It works, but:
- photos, videos and most PDFs barely shrink when zipped,
- the recipient has to collect every part before anything opens,
- one missing email means the whole set is useless.
3. Send a transfer link
Upload the file to a transfer service and paste the link into your email. With Enzonic Send:
- Drag the file or a whole folder into the uploader on this page. Folders and multiple files are zipped in your browser, with their structure kept.
- Choose an expiry: 1 hour, 1 day or 3 days without an account, up to 7 days with a free account.
- Optionally add a password, a download limit, and a title and message.
- Copy the link and paste it into Outlook.
No account is needed up to 500 MB per transfer. A free account raises that to 2 GB. The recipient does not need an account at all.
Keeping business files under control
Attachments live forever in Sent Items and the recipient's inbox, plus any backups. For contracts, invoices and anything with personal data, a link with limits gives you more control:
- Expiry: files auto-delete when the link expires. You can also delete them yourself at any time.
- Password: send the password by phone or text, not in the same email as the link.
- Download limit: set it to 1 if only one person should ever download it.
Transfers are encrypted in transit and at rest. They are not end-to-end encrypted, so for regulated data stick to the tools your organisation has approved. See password-protected file sharing and expiring file links for how those options work.
Troubleshooting checklist
- Error appears when attaching: your total is over the limit. Remove files or switch to a link.
- Email stuck in Outbox: Outlook desktop may keep retrying a message that is too large. Delete it from the Outbox and resend with a link.
- Bounce message from the recipient's server: their limit is lower than yours. Send a link.
- Link in the email is broken or rewritten: some corporate mail filters rewrite URLs. Give the recipient the 6-digit code and point them to send.enzonic.com/receive.
- Recipient cannot open the file: check they have an app for that file type. Zipped folders open natively on Windows and Mac.
Outlook vs Gmail
Gmail's cap is a little higher at 25 MB, but the same encoding overhead and recipient-side limits apply, and big files get pushed into Google Drive. The Gmail attachment size limit guide covers that side. For a broader look at moving big files, including cloud drives and device-to-device options, read how to send large files free or files too big for email.
FAQ
What is the attachment size limit in Outlook?
At the time of writing, Outlook.com and the Outlook desktop app typically allow up to 20 MB per message. Work or school accounts on Exchange may have a different limit set by the IT admin.
What does 'attachment size exceeds the allowable limit' mean?
The total of all attachments in the message is over the limit your account or mail server allows. Remove some files, or send them as a link instead.
Can I change the Outlook attachment limit myself?
Not on Outlook.com. On corporate Exchange or Microsoft 365, the limit is set by your organisation's admin, so you would need to ask them.
Why did my email send but the recipient never got it?
The recipient's mail server may have a lower incoming limit than yours. Large attachments can bounce or be silently dropped on their side.
Does Outlook offer to upload big files to OneDrive?
Outlook can share files from OneDrive as links, which avoids the attachment limit. The file then lives in your OneDrive and uses your storage until you delete it.
Updated 2026-10-17